A NICKEL-CATALYZED CARBOZINCATION OF ARYL-SUBSTITUTED ALKYNES

The addition of dialkylzincs or diphenylzinc to substituted phenylacet ylenes in the presence of catalytic amounts of Ni(acac)(2) in THF : NM P mixtures produces syn-carbozincation products with good to excellent regio-and stereoselectivity. After quenching with an electrophile (io dine, acyl chloride, allyl bromide) tetrasubstituted olefines are obta ined in good to satisfactory yields. An intramolecular version of the reaction is possible using a terminal triple bond bearing an iodine at a remote position. More substituted iodo-alkynes furnish only reducti ve elimination products. An application to a stereoselective synthesis of (Z)-tamoxifen (Z: E > 99: 1) has been developed. (C) 1998 Elsevier Science Ltd. All rights reserved.